基于AVR单片机的超声波测距系统构建

为了提高超声波测距精度,构建了基于AVR单片机的测距及数据处理系统。分析了超声波测距的原理,以AVR单片机为处理器设计了超声波产生和发射电路、超声波接收和信号处理电路以及温度测量和补偿电路等。针对温度对超声波速度的影响,根据超声波速度与温度的关系,设计了超声波速度补偿算法。为了提高回波时间测量准确性,减小随机噪声及空气中其他杂散播干扰的影响,采用均值数字滤波方法,对计数时间进行处理。实测结果表明,在3cm~400cm范围内,超声波测距系统测量数据准确,最大误差为0.66cm。     

光纤布拉格光栅在冰声学性能测量中的应用

以光纤布拉格光栅检测动态应变为基础,分析了匹配型光纤布拉格光栅波长移动解调方案的基本原理。利用匹配光栅法检测的高灵敏性及光纤光栅传感器本身的优点,将其与超声波检测相结合,创新性地用于研究超声波在冰样中的传播速度随温度的变化关系,通过光纤布拉格光栅检测冰样中纵波、横波传播速度与温度的关系,利用Matlab对数据进行拟合及计算,得到了冰样的声学参数随温度变化的规律:温度越低,超声波在冰样中的传播速度越高。并将所测数据与超声波系统所测数据进行对比,结果表明,光纤布拉格光栅所测数据正确可靠,证明了光纤布拉格光栅可用于检测冰的声学性能。     

喷流耦合式超声位移传感器的设计

本文主要研究一种新型微位移传感器。它用超声波原理进行检测，以喷流的水柱作为超声波传播的介质，可以在恶劣环境下进行位移测量。位移等于超声波传播的速度与超声波从发到收之间传播时间的乘积。考虑到声速会随介质一水的温度的升高而增大，设计时进行了实时温度补偿，提高了系统的精度。     

航空透明件表面波声弹效应

表面波作为超声波的一种特殊形式,由于其传播特性,使得通过改变频率检测距物体表面不同深度处的;初邕应力成为可能,因此,各种产表面波声弹理论与实验技术的研究不断受到重视。本文从弹性波和有限变形理论出发,推导了表面波在有初始应力的各同性弹性体中传播时,物体表面应力与超声波传播速度之间的一般关系。对作为收音机坐舱的航空透年ＹＢ－３有机玻璃试件进行了声弹性实验。同时还给出了由实验数据回归的三次多项式声弹公式     

溶剂和超声波快速制备β-D-葡萄糖的研究

本文研究了，利用溶剂和超声波的协同作用，在较缓和的条件下快速制备β－Ｄ－葡萄糖的方法，研究内容主要包括成核溶剂的挑选，以及葡萄糖溶液浓度，温度，超声电功率密度辐照时间等因素的组合对成核晶型的影响，获得了快速制备β－Ｄ－葡萄糖的最佳组合条件，并提出了超声波协同溶剂影响成核晶型的机理，为超声空化泡崩溃时产生的“热点效应”。     

基于超声波飞行时间的温度测量系统实验研究

超声波测量技术具有速度快、成本低、测量范围广等优点,广泛应用于多种工业领域。为满足工业中对温度测量的需求,本文提出了超声波温度测量系统。本系统基于超声波的传播速度与环境温度的关系,以STC12单片机作为系统硬件电路控制核心,采用幅度和相位调制的矩形波作为发射波,实现在恒温箱空气介质中固定距离下的超声波飞行时间的测量,以此确定介质的平均温度。测量数据由单片机传输到上位机进行处理和显示,并与恒温箱热电偶测得的温度对照,验证实验结果。实验结果证明本系统可以准确测量温度,温度范围约在35℃—90℃。     

纵横波测已紧固螺栓轴向应力

本提出了用纵横波声时测已紧固螺栓轴向应力的一种新方法,解决了用超声精确地测已紧固螺栓应力问题,并且利用超声波沿轴向传播的波速同轴向应力以及三阶弹性常数的关系导出了螺栓应力同其材料声速特性、夹紧距离、温度及纵、横波声时的一种新关系,考虑了受应力作用时温度对声速的影响,简化了测量及计算过程,本还介绍了材料的声速特性实验及测量方法;实验结果表明应力低于２５０ＭＰａ,夹紧距离大于３０ｍｍ时,应力超声测     

用于彩色滤光片的低阻低应力ITO透明导电膜

探讨了用于彩色滤光片的低电阻和低压应力的ITO透明导电膜工艺。用磁控溅射方法在不同温度的衬底上制备了ITO薄膜。研究了膜形衬底温度与膜结晶化程度的关系,以及膜形衬底温度对膜电阻和压应力的影响。对不同衬底温度下形成的ITO薄膜进行了退火处理,并对退火后的ITO薄膜的电阻和压应力特性进行了分析。结果表明,采用室温沉积非晶态ITO膜,在真空退火下可获得低电阻、低压应力的多晶相ITO膜。     

声光衍射测量声速的教学应用

声光衍射的方法测量超声波在液体中的速度是非常实用的方法,实验教学中也应用广泛。教学过程中,由于学生测量的误差较大,使得计算出来的速度值与理论值相差甚大,因此本实验改进了声光衍射的实验方法,利用IDL(interactive data language)软件精确测量数据,提高实验的准确性,得出超声波在纯水中的传播速度随温度的变化情况。     

基于超声波飞行时间的空气温度场重建

利用超声波在空气中的传播速度会随着空气温度的变化而变化这一特点,可测得空气中不同温度下的平均速度场,进而重建空气中的温度场。提出了一种非对称布置超声波传感器重建二维温度场的方法,在被测温度场周围布置8个收发一体的超声波传感器,并将被测温度场划分为24个小区间,以得到超声波通过每个小区间的平均温度值,以该温度值作为小区间中心点的温度并进行插值,从而重建整个被测区域的温度场。     

Hydrostatic pressure and temperature calibration based on phase diagram of bismuth

Under high-temperature and high pressure (HTHP) experiments, materials of small elastic modulus deform easily, and the length of the sample can be hardly predicted which lead to failure of ultrasonic velocity measurement. In this paper, a hydrostatic assembly of the sample for ultrasonic measurements is designed under HPHT, which can prevent plastic deformation. According to the abrupt change of travel time of the sample across the different phase boundaries of bismuth, the correspondent relation of sample pressure and oil pressure of multi-anvil apparatus can be calibrated, and the relation of sample temperature and temperature measured by thermocouple can also be determined. Sample pressure under high temperature is also determined by ultrasonic results. It is believed that the new sample assembly of hydrostatic pressure is valid and feasible for ultrasonic experiments under HTHP.     

Estimation of clamping force in high-tension bolts through ultrasonic velocity measurement

The estimation of clamping force has been regarded as the main issue in the maintenance of high-tension bolts. This paper proposes a method which uses the dependency of ultrasonic velocity on stress based on the nonlinear elastic effect. The variation of ultrasonic velocity in the range of actual stress acting in the bolt is very small so that the precise measurement of ultrasonic velocity is needed. In this paper, we adopt a method to measure ultrasonic velocity, where the TOF (time of flight) of a tone-burst ultrasonic wave is precisely measured by using the phase detection technique. In order to verify the usefulness of the proposed method, two kinds of experiments are carried out. The first one measures ultrasonic velocity when the bolt is stressed by the tension tester, and from this, the exact axial force acting in the bolt can be determined. The results show good agreement with the expected linear relationship between ultrasonic velocity and axial stress. The second experiment measures ultrasonic velocity when the bolt is stressed by the torque wrench. The results show that ultrasonic velocity decreased as the torque increased, which is identical to the theoretically expected tendency. From these results, it can be said that the proposed method is adequate in evaluating clamping force in high-tension bolts.     

Acoustoelastic evaluation of arbitrary plane residual stress states in non-homogeneous, anisotropic plates

In this paper it is shown that relative ultrasonic velocity measurements can be used to determine the difference of normal stress components (T₂₂ − T₁₁) in non-homogeneous, anisotropic plates containing arbitrary residual stress states. It has previously been demonstrated that measurements with horizontally polarized shear waves (SH-waves) can be used to determine (T₂₂ − T₁₁) unambiguously in plates with unknown material property variations. However, previously the theory relating the velocity of SH-waves to stress and material anisotropy was limited to the case where the principal directions of stress are parallel to the axes of material symmetry. In this paper, we remove this restriction by extending the theory. We also suggest possible experimental procedures for validating the new theory.     

二元有机混合液声速温度系数(C/T)P

依据Jacobson液体分子自由程理论及液体声速与分子自由程关系,推导出二元有机混合液的声速温度系数表达式.由此计算出的二元有机混合液的声速温度系数值与实验值符合较好. 关键词：     

A study of nanosized zinc oxide and its nanofluid

The synthesis and characterization of nanosized zinc oxide and its nanofluid in a polyvinyl alcohol (PVA) matrix have been done in the present investigation. Crystalline zinc oxide nanoparticles are synthesized using single-step chemical method while the nanofluids are prepared by the dispersion of nanoparticles in PVA solution using an ultrasonicator. The prepared nanoparticles are characterized using X-ray diffraction, SEM?CEDX and UV?Cvisible spectrum. The particle size distribution measurement is carried out by acoustic particle sizer. The ultrasonic velocities are measured in the synthesized nanofluid under different physical conditions using an ultrasonic interferometer. It is found that the degree of crystallinity of nanoparticles depends on the evaporation rate during its synthesis and ultrasonic velocity has non-linear relation with temperature for the present nanofluid.     

Ultrasonic SH wave velocity in textured aluminium plates

Neutron diffraction has been used to measure the crystallite orientation distribution function for a sample of rolled aluminium plate. Based on this study an expression is given for the ultrasonic velocity of the fundamental horizontally polarized shear (SH) wave propagating in the plane of the plate at an angle θ to the rolling direction. This expression is correct to second order in the leading texture component and is compared with the exact numerical result and with measurements of the SH wave velocity for this plate. In textured materials the group and phase velocities are not, in general, parallel and an expression for the angle between them is derived. Inclusion of this effect leads to better agreement between experiment and theory. The results have application to the texture-independent determination of stress with ultrasonics recently proposed by MacDonald and Thompson et al.     

外部流场对激光加热运动目标影响的数值模拟

 考虑激光与运动目标相互作用的基础上，利用有限元方法分析了亚声速条件下运动目标在激光辐照全过程的温度场和热应力场的分布与演化规律。结果表明：高速流场的存在，导致了明显的冷却效应；加热过程中目标材料出现了屈服，导致激光熄灭后结构内出现残余应力和变形；激光辐照区边缘产生很高的温度梯度和应力梯度，并且由于气流影响，受辐照区域前后两端应力分布不对称。